Hydrocracking catalyst

ABSTRACT

Process for preparing a hydrocracking catalyst carrier which process comprises subjecting a carrier comprising an amorphous binder and zeolite Y having a silica to alumina molar ratio of at least 10 to calcination at a temperature of from 700 to 900° C., hydrocracking catalyst carrier comprising amorphous binder and zeolite Y having a silica to alumina molar ratio of at least 10, the infrared spectrum of which catalyst has a peak at 3690 cm −1 , substantially reduced peaks at 3630 cm −1  and 3565 cm −1  and no peak at 3600 cm −1 , hydrocracking catalyst carrier comprising an amorphous binder and zeolite Y having a silica to alumina molar ratio of at least 10, which catalyst has an acidity as measured by exchange with perdeuterated benzene of at most 20 micromole/gram, hydrocracking catalyst derived from such carrier and hydrocracking process with the help of such catalyst.

The present application is a divisional of U.S. Non Provisionalapplication Ser. No. 13/266,713, filed Oct. 27, 2011, which is a 35U.S.C. §371 national stage filing of PCT/EP2010/054934 filed 15 Apr.2010, which claims priority from European Application 09159007.5, filed29 Apr. 2009 incorporated herein by reference.

The present invention relates to a hydrocracking catalyst andhydrocracking catalyst carrier and processes for preparing those, and ahydrocracking process.

BACKGROUND OF THE INVENTION

Processes that comprise treating crude oil and other petroleumfeedstocks with hydrogen in the presence of a catalyst are well known.One such process is hydrocracking, in which heavy distillatehydrocarbons are converted under hydrogen pressure into products oflower molecular weight in the presence of a catalyst. Hydrocracking isused in the oil industry to prepare a wide range of materials, rangingfrom C3/C4 production to luboil manufacture.

Hydrocracking may be operated as either a single or two-stage process.Two-stage hydrocracking involves a first stage, which is predominantly ahydrotreatment stage wherein impurities and unsaturated compounds arehydrogenated in the presence of a first catalyst having a highhydrogenation function, and a second-stage where most of the crackingoccurs in the presence of a second catalyst having a strong crackingfunction. In single-stage hydrocracking, the treatment and crackingsteps occur in one reactor and may be performed using a single catalyst.The catalysts employed in hydrocracking are generally made from acarrier material on which there are deposited catalytically activemetals such as nickel, molybdenum, tungsten and palladium.

It is advantageous to have a catalyst which enables the refinery toproduce the most attractive product slade for the refinery in question.A product slade which can be advantageous is one having an increased gasoil yield. Gas oils are hydrocarbons boiling in the range of from 250 to370° C. at atmospheric pressure, and are suitable for use as diesel.Especially in Europe and Asia, there tends to be an increased demand fordiesel and reduced demand for gasoline. Further, an improveddenitrogenation was observed.

SUMMARY OF THE INVENTION

It has now surprisingly been found that a catalyst having a higherselectivity for gas oil can be obtained in a simple and efficient way bycalcining a carrier comprising amorphous binder and zeolite Y at arelatively high temperature. The catalyst was further found to haveimproved denitrogenation properties.

Accordingly, the present invention provides a process for preparing ahydrocracking catalyst carrier which process comprises subjecting acarrier comprising an amorphous binder and zeolite Y having a silica toalumina molar ratio of at least 10 to calcination at a temperature offrom 700 to 900° C. Furthermore, the present invention relates tohydrocracking catalyst carrier obtainable by such process.

Prior art documents such as WO2004047988 and WO2005084799 mention abroad temperature range for calcining a catalyst carrier. However,someone skilled in the art would not seriously consider use of the fullrange especially as a high temperature is suspected of breaking down thezeolitic structure. Someone skilled in the art would only consider arelatively narrow range of the full temperature range of 300 to 800° C.mentioned in WO2004047988 or 300 to 850° C. mentioned in WO2005084799namely a range close to the calcination temperature actually applied,i.e. 535° C.

Further, it was found that the hydrocracking catalyst carriers obtainedby the process of the present invention, differ from known hydrocrackingcatalysts in their infrared spectrum. Therefore, the present inventionfurther relates to hydrocracking catalyst carriers comprising anamorphous binder and zeolite Y having a silica to alumina molar ratio ofat least 10, the infrared spectrum of which carrier has a peak at 3690cm⁻¹, substantially reduced peaks at 3630 cm⁻¹ and 3565 cm⁻¹ and no peakat 3600 cm⁻¹ and to hydrocracking catalyst comprising a Group VIIImetal, a Group VIB metal and such carrier.

Furthermore, it was found that a specific kind of acidity of thecatalysts obtained by the process of the present invention is less thanthe acidity of known catalysts. Therefore, the present invention alsorelates to hydrocracking catalyst carrier which comprises an amorphousbinder and zeolite Y having a silica to alumina molar ratio of at least10, which carrier has an acidity as measured by exchange withperdeuterated benzene of at most 20 micromole/gram, and to hydrocrackingcatalyst comprising a Group VIII metal, a Group VIB metal and suchcarrier. It is especially surprising that carrier comprising zeolite Yhaving a reduced acidity gives increased gas oil selectivity at the sameactivity. Reduced acidity conventionally results in reducedhydrocracking activity.

DETAILED DESCRIPTION OF THE INVENTION

The calcination of the catalyst carrier is carried out at a temperatureof from 700 to 900° C. The time during which the catalyst is calcinedinfluences the exact temperature to be applied. Generally, thetemperature is at most 850° C. At a calcination temperature of more than900° C., loss of crystallinity of the zeolite Y was observed. The timeduring which the catalyst carrier is calcined preferably is of from 20minutes to 5 hours, more preferably of from 30 minutes to 4 hours. Thetime period to be applied further depends on whether the oven ispreheated or whether the temperature is increased while the catalystcarrier is being calcined. The time period preferably is at least 40minutes, more preferably at least 50 minutes. Further, the time periodis preferably less than 4 hours, more preferably less than 3½ hours. Thetemperature preferably is at most 850° C., more preferably at most 820°C., most preferably at most 800° C.

The calcination can be carried out in the presence or in the absence ofan inert gas such as steam, and at reduced, ambient or increasedpressure. Preferably, the calcination is carried out in air at ambientpressure.

The catalyst carrier can be calcined according to the present inventionafter the catalytically active metals have been deposited. However, thisis generally disadvantageous as the high calcination temperature willtend to lead to maldistribution of the catalytically active metal.Therefore, it is preferred that carriers are prepared according to thepresent invention and subsequently impregnated with a Group VIII metaland a Group VIB metal. The thus impregnated carriers are then generallycalcined again but this time at a temperature of from 300 to 700° C.,more specifically of from 400 to 600° C.

Preferred zeolite Y materials for use in the present invention arezeolite Y having a silica to alumina ratio (SAR) of more than 10,especially an ultrastable zeolite Y (USY) or a very ultrastable zeoliteY (VUSY) of unit cell size (a_(O)) less than 2.440 nm (24.40 Ångstroms),in particular less than 2.435 nm (24.35 Ångstroms) and a SAR of morethan 10, specifically of more than 10 up to 100. Suitable zeolite Ymaterials are known, for example, from EP247678 and EP247679, andWO2004047988.

Whilst USY and VUSY Y zeolites are preferred for use in the presentinvention, other Y zeolite forms are also suitable for use, for examplethe known ultrahydrophobic Y zeolites.

Preferred VUSY zeolite of EP247678 or EP247679 is characterised by aunit cell size below 2.445 nm (24.45 Ångstroms) or 2.435 nm (24.35Ångstroms), a water adsorption capacity (at 25° C. and a p/p_(O) valueof 0.2) of at least 8% wt of the zeolite and a pore volume of at least0.25 ml/g wherein between 10% and 60% of the total pore volume is madeup of pores having a diameter of at least 8 nm.

Most preferred are the low unit cell size, high surface area zeolite Ymaterials described in WO2004047988. Such materials can be described asa zeolite Y having a SAR above 12, a unit cell size in the range of from24.10 to 24.40 Å, and a surface area of at least 850 m²/g as measured bythe BET method and ATSM D 4365-95 with nitrogen adsorption at a p/povalue of 0.03. Said materials can be prepared by a process whichcomprises

-   a) providing a starting zeolite of the faujasite structure having a    silica to alumina ratio of from 4.5 to 6.5 and an alkali level of    less than 1.5% wt;-   b) hydrothermally treating said starting zeolite at a temperature in    the range of from 600 to 850° C., preferably 600 to 700° C. more    preferably 620 to 680° C. and especially 630 to 670° C., and at a    partial pressure of, preferably externally supplied, steam in the    range of from 0.2 to 1 atmosphere for a time effective to produce an    intermediate zeolite having a unit cell size of from 24.30 to 24.45    Å, being suitably in the range of from 0.5 to 5 hours, more suitably    1 to 3 hours;-   c) contacting the intermediate zeolite with an acidified solution    comprising an acid and optionally an ammonium salt under conditions    effective to produce a high surface area zeolite having a unit cell    size in the range of from 24.10 to 24.40 Å, a molar silica to    alumina ratio of greater than 12 and a surface area of greater than    850 m²/g, thereby producing the high surface area zeolite; and-   d) recovering said high surface area zeolite.

Especially preferred high surface area materials have one or more of thefollowing features:

-   -   unit cell size in the range of from 24.14 to 24.38, preferably        from 24.24, more preferably from 24.30, to 24.38, preferably to        24.36, especially to 24.35 Å, and specifically in the range of        from 24.14 to 24.33 Å;    -   a SAR in the range of from 20 to 100, preferably from 20 to 80,        especially to 50; surface area of at least 875, preferably at        least 890, specifically at least 910 m²/g; a micropore volume,        as determined by nitrogen porosimetry using the t-plot method,        also known as the t-method, using nitrogen as the adsorbate as        described by Lippens, Linsen and de Boer, Journal of Catalysis,        3-32, (1964), of greater than 0.28 ml/g, suitably greater than        0.30 ml/g. Generally micropore volume will be less than 0.40        ml/g, suitably less than 0.35 ml/g. Herein micropores are pores        having a diameter of less than 2 nm.

It is possible, and may be preferred in certain cases, for the carrierof the present invention to include an additional zeolite besideszeolite Y described above. Most preferably, the additional zeolite isselected from zeolite beta, zeolite ZSM-5, or a zeolite Y having a unitcell size and/or SAR other than described above. The additional zeolitepreferably is zeolite beta. The additional zeolite can be present in anamount of up to 20% wt, based on total carrier, but preferably theadditional zeolite is present in an amount in the range of from 0.5 to10% wt.

The amount of all zeolite in the carrier of the invention is usefully inthe range of from 2 to 70% wt based on total carrier with the amount ofamorphous binder being of from 98 to 30% wt. Preferably, the amount ofall zeolite in the carrier is in the range of from 5 to 50, especiallyfrom 10 to 50% wt based on total carrier.

The amorphous binder may be any refractory inorganic oxide or mixture ofoxides conventional for such compositions. Generally this is an alumina,a silica, a silica-alumina or a mixture of two or more thereof. Howeverit is also possible to use zirconia, clays, aluminium phosphate,magnesia, titania, silica-zirconia and silica-boria, though these arenot often used in the art. The amorphous binder most preferably issilica-alumina. The amorphous silica-alumina preferably contains silicain an amount in the range of from 25 to 95% by weight as calculated onthe carrier alone (i.e. based on total carrier). More preferably theamount of silica in the carrier is greater than 35% wt, and mostpreferably at least 40% wt. A very suitable amorphous silica-aluminaproduct for use in preparing the catalyst carrier of the inventioncomprises 45% by weight silica and 55% by weight alumina and iscommercially available (ex. Criterion Catalysts and Technologies, USA).

In the preparation of the catalyst carrier of the invention, followingthe mixing of binder and zeolite Y, optionally in combination withadditional zeolite, an acidic aqueous solution maybe added to themixture after which it is mulled, extruded and calcined in conventionalmanner Any convenient mono-basic acid may be used for the acidicsolution; examples are nitric acid and acetic acid. During extrusion,conventionally extrusion aids are utilized; usual extrusion aids includeSuperfloc, obtainable from Nalco.

It is preferred that the carrier is prepared by shaping a mix comprisingamorphous binder and zeolite Y, optionally in combination withadditional zeolite, wherein the mix has a loss of ignition (LOI) in therange of from 55 to 65%. It has been found that such LOI gives a carrierhaving an especially advantageous pore size distribution namely amonomodal pore size distribution wherein at least 50% of the total porevolume is present in pores having a diameter in the range of from 4 to50 nm and wherein the pore volume present in said pores is at least 0.4ml/g, all as measured by mercury intrusion porosimetry. The effect ofthis high mesopore pore volume is that the compacted bulk density (CBD)of the catalyst carrier becomes greatly reduced. A further advantage isthat such carrier was found to give catalysts having an increasedactivity that was maintained over time. Further details on thepreparation process and on the carriers obtained are given inWO2005084799.

Extrusion may be effected using any conventional, commercially availableextruder. In particular, a screw-type extruding machine may be used toforce the mixture through orifices in a die plate to yield catalystextrudates of the required form, e.g. cylindrical or trilobed. Thestrands formed on extrusion may then be cut to the appropriate length.If desired, the catalyst extrudates may be dried, e.g. at a temperatureof from 100 to 300° C. for a period of 30 minutes to 3 hours, prior tocalcination.

The present invention also relates to carriers according to the presentinvention having an acidity as measured by exchange with perdeuteratedbenzene of at most 20 micromole/gram. This acidity more preferably is atmost 15, more preferably at most 12, more preferably at most 10 and mostpreferably at most 8 micromole/gram.

The catalysts derived from the carriers according to the presentinvention preferably have at least one hydrogenation componentincorporated. This addition may occur at any stage during catalystpreparation, using techniques conventional in the art. For example, thehydrogenation component can be added to the zeolite, or a mixture ofzeolite and binder, through co-mulling. Alternatively the hydrogenationcomponent may be added to the formed extrudates either before or aftercalcining, using conventional impregnation techniques, e.g. as one ormore aqueous impregnating solutions of Group VIB and/or Group VIII metalsalts. If the impregnation occurs after calcination of the formedextrudates, then a further drying and calcination procedure is usefullyemployed. Preferably, the calcined carrier is subsequently impregnatedwith a Group VIII metal and a Group VIB metal. The present inventionalso refers to hydrocracking catalyst obtainable thereby.

Herein reference is made to the Periodic Table of Elements which appearson the inside cover of the CRC Handbook of Chemistry and Physics (‘TheRubber Handbook’), 66^(th) edition and using the CAS version notation.

Suitably the hydrogenation component is selected from the groupconsisting of nickel, cobalt, molybdenum, tungsten, platinum andpalladium.

Examples of hydrogenation components that may thus suitably be usedinclude Group VIB (preferably molybdenum and/or tungsten) and Group VIIImetals (preferably cobalt, nickel, iridium, platinum and/or palladium),their oxides and sulphides. The catalyst composition will preferablycontain at least two hydrogenation components, more specifically amolybdenum and/or tungsten component in combination with a cobalt and/ornickel component. Particularly preferred combinations arenickel/tungsten and nickel/molybdenum. Very advantageous results areobtained when these metal combinations are used in the sulphide form.

The catalyst according to the present invention may contain up to 50parts by weight of hydrogenation component, calculated as metal per 100parts by weight (dry weight) of total catalyst composition. For example,the catalyst composition may contain from 2 to 40, more preferably from5 to 30 and especially from 10 to 20, parts by weight of Group VIBmetal(s) and/or from 0.05 to 10, more preferably from 0.5 to 8 andadvantageously from 1 to 6, parts by weight of Group VIII metal(s),calculated as metal per 100 parts by weight (dry weight) of totalcatalyst composition.

The present invention also provides a hydrocracking process forconverting a hydrocarbon feedstock into lower boiling materials whichcomprises contacting the feedstock with hydrogen at elevated temperatureand elevated pressure in the presence of a hydrocracking catalystaccording to the present invention.

Examples of such processes comprise single-stage hydrocracking,two-stage hydrocracking, and series-flow hydrocracking. Definitions ofthese processes can be found in pages 602 and 603 of Chapter 15,entitled “Hydrocarbon Processing with Zeolites” of “Introduction toZeolite Science and Practice”, edited by van Bekkum, Flanigen, Jansen,published by Elsevier, 1991.

It will be appreciated that the hydrocracking processes of the presentinvention can be carried out in any reaction vessel usual in the art.Thus the process may be performed in a fixed bed or moving bed reactor.Also the catalyst of the invention may be used in conjunction with anysuitable co-catalyst or other materials usual in the art. Thus forexample the catalyst of the invention may be used in stacked bedformation with one or more other catalysts useful in hydroprocessing,for example with a catalyst containing a different zeolite, with acatalyst containing a faujasite zeolite of different unit cell size,with a catalyst utilizing an amorphous carrier, and so on. Variousstacked bed combinations have been proposed in the literature:WO9932582, EP0310164, EP0310165, and EP0428224.

The hydrocarbon feedstocks useful in the present process can vary withina wide boiling range. They include atmospheric gas oils, coker gas oils,vacuum gas oils, deasphalted oils, waxes obtained from a Fischer-Tropschsynthesis process, long and short residues, catalytically cracked cycleoils, thermally or catalytically cracked gas oils, and syncrudes,optionally originating from tar sand, shale oils, residue upgradingprocesses and biomass. Combinations of various hydrocarbon oils may alsobe employed. The feedstock will generally comprise hydrocarbons having aboiling point of at least 330° C. The boiling range will generally befrom about 330 to 650° C., with preference being given to feedstockshaving a boiling range of from about 340 to 620° C. The feedstock mayhave a nitrogen content of up to 5000 ppmw (parts per million by weight)and a sulphur content of up to 6% w. Typically, nitrogen contents are inthe range from 250 to 2000 ppmw and sulphur contents are in the rangefrom 0.2 to 5% w. It is possible and may sometimes be desirable tosubject part or all of the feedstock to a pre-treatment, for example,hydrodenitrogenation, hydrodesulphurisation or hydrodemetallisation,methods for which are known in the art.

The process of the invention may conveniently be carried out at areaction temperature in the range of from 250 to 500° C., preferably inthe range of from 300 to 450° C.

The present process is preferably carried out at a total pressure (atthe reactor inlet) in the range of from 3×10⁶ to 3×10⁷ Pa, morepreferably from 4×10⁶ to 2.5×10⁷ Pa and even more preferably from 8×10⁶to 2×10⁷ Pa. Where a hydrocracking process is carried out at a lowpressure such as of from 4×10⁶ to 1.2×10⁷ Pa, this may be termed ‘mildhydrocracking’.

The hydrogen partial pressure (at the reactor inlet) is preferably inthe range from 3×10⁶ to 2.9×10⁷ Pa, more preferably from 4×10⁶ to2.4×10⁷ Pa and still more preferably from 8×10⁶ to 1.9×10⁷ Pa.

A space velocity in the range from 0.1 to 10 kg feedstock per litrecatalyst per hour (kg·l⁻¹ h⁻¹) is conveniently used. Preferably thespace velocity is in the range from 0.1 to 8, particularly from 0.2 to 5kg·l⁻¹·h⁻¹.

The ratio of hydrogen gas to feedstock (total gas rate) used in thepresent process will generally be in the range from 100 to 5000 Nl/kg,but is preferably in the range from 200 to 3000 Nl/kg.

The present invention will now be illustrated by the following Examples.

Examples

In the Examples the following test methods have been used:

Unit cell size: Determined by X-ray diffraction using the method of ASTMD-3942-80.Surface Area: Determined in accordance with the conventional BET(Brunauer-Emmett-Teller) method nitrogen adsorption technique asdescribed in the literature at S. Brunauer, P. Emmett and E. Teller, J.Am. Chm. Soc., 60, 309 (1938), and ASTM method D4365-95.Silica to alumina molar ratio (SAR): Determined by chemical analysis;values quoted are ‘bulk’ SAR (that is to say the overall SAR) and notspecifically the SAR of the zeolite.

Carrier Preparation

The zeolite Y utilised in the catalysts of the present invention wasprepared in accordance with the teaching of WOA2004047988. The startingmaterial used was low alkali content (<1.5% wt alkali oxide) ammoniumform Y zeolites. These zeolites were prepared by one of two methodsknown in the art. The examples were prepared either according to theteaching of U.S. Pat. No. 5,435,987 which involves K ion exchange of Naform zeolite Y, followed by ammonium ion exchange, or according to theteaching of U.S. Pat. No. 4,085,069 which involves ammonium exchangeunder autogenous superatmospheric pressure. The low alkali contentammonium form Y zeolite was steam calcined in one or two steps to createan ultrastable type Y zeolite. The steamed zeolites were then subjectedto an acid-dealumination treatment consisting of a one step treatmentwith a combination of ammonium chloride and hydrochloric acid. The watercontent in the ion-exchange-dealumination treatment was generallysufficient to provide a zeolite slurry with from 5 to 25% anhydrouszeolite. Such variation is not believed to materially affect the resultsobtained.

The zeolite Y obtained had a silica to alumina molar ratio of 25, a unitcell size of 24.33 A and a surface area of 922 m²/g.

The zeolite Y was mixed with amorphous silica-alumina comprising 45% byweight silica and 55% by weight alumina commercially available ex.Criterion Catalysts and Technologies, USA.

The zeolite beta is commercially available from Zeolyst International,USA. It was added in the proportions required. The % wt indicated inTables 1 and 2 are the weight amounts on total weight of dry carrier.Water and 3% wt nitric acid (65% wt solution) were added in order toachieve a pH in the range of from 4.4 to 5.7 and a loss of ignition offrom 50 to 60% wt and the mixture mulled in a mix-muller until anextrudable mix was obtained. The mixture was then extruded, togetherwith an extrusion aid (Superfloc), into extrudates having, incross-section, a trilobe shape. A 3 to 5 cm layer of extrudates wasdried stationary in an air ventilated drying furnace overnight at 120°C. A 1 cm thick layer of the carrier particles so obtained was placed ina perforated metal basket and calcined stationary in an air ventilatedmuffle furnace by heating from room temperature to the temperatureindicated at a speed of 6° C. per minute and kept there for 2 hours. Nosteam is added. After calcination the particles are allowed to cool downin the furnace to 250° C. before removal. The catalyst particles had adiameter of 1.6 mm, measured from the top to the bottom of a nominaltriangle formed by the tri-lobe. Table 1 shows physical properties ofhydrocracking catalyst carriers obtained in this way.

TABLE 1 Carrier 1 2 3 4 Calcination (° C.) 620 750 620 750 Surface area(m²/g) 536 521 505 504 Unit cell size (nm) 2.434 2.432 2.434 2.433Zeolite Y content (% w) 30.3 29.5 22.5 21.7 Zeolite beta content (% w) —— 5.3 7.9 H/D (acidity in micromole/gram) 31.3 6.4 24.6 5.2

Infrared Spectrum

The IR spectrums of the above catalyst carriers were measured with thehelp of a Biorad FTS175 FT-IR spectrometer using a mercury cadmiumtelluride detector. The cell is equipped with a sample holder comprising10 positions and samples have been measured as self-supporting waferswith a diameter of 18 mm, pressed from 25.3+/−0.1 mg zeolite powder at3.5-4 Ton pressure. For the background measurement an open position ofthe sample holder has been used. Background and sample spectra have beenmeasured by collecting 250 scans at 2 cm⁻¹ resolution. The spectrometeris flushed with nitrogen to minimize the interference of water vapor.After evacuating to less than 5×10⁻⁴ mbar, samples have been activatedin situ in a special heating zone by applying a temperature program oframping to 450° C. at a rate of 10° C./min, with a hold time of 30minutes at 450° C. Subsequently, samples have been cooled to 50° C. with20° C./min. Then background and sample IR spectra have been measured.

The infrared spectrum of carriers 1 and 3 had peaks at 3630 cm⁻¹ and3565 cm⁻¹ and a broad peak centred at 3600 cm⁻¹. There was no peak at3690 cm⁻¹.

The infrared spectrums of carriers 2 and 4 had a peak at 3690 cm⁻¹ and asubstantially reduced peak at 3630 cm⁻¹ and 3565 cm⁻¹ and no peak at3600 cm⁻¹.

H/D Acidity

After evacuating to less than 5×10⁻⁴ mbar, samples have been activatedin situ in a special heating zone by applying a temperature program oframping to 450° C. at a rate of 10° C./min, with a hold time of 30minutes at 450° C. Subsequently, samples have been cooled to 50° C. with20° C./min. Then background and sample IR spectra were measured.

After recording the above-mentioned IR spectra, the sample holder isslided back to the heating zone, and equilibrated at 50° C. for anadditional 15 min, while the vacuum was maintained. H/D exchange wasperformed in situ by letting 8-9 Torr of hexadeuterobenzene (C₆D₆)interact with the activated zeolite samples for 15 min at 50° C.followed by evacuation for 45 minutes to a target pressure of 5×10⁻⁴mbar (with a maximum of 1 hour). Then background and sample IR spectrawere measured.

To quantify the total amount of acidity, the IR spectra of the samplebefore (OH spectrum) and after (OD spectrum) contact withhexadeuterobenzene were compared as follows. The obtained OH spectrumwas subtracted from the OD spectrum and baseline corrected. Thencurve-fitting was performed with a predefined peak set for VUSY typematerials and previously determined extinction coefficients.

Catalyst Preparation

The metal hydrogenation components nickel and tungsten were incorporatedin extrudates prepared as described above by impregnation of theextrudates with anhomogenized aqueous solution of nickel nitrate andammonium metatungstate to which furthermore citric acid was added. Theimpregnated extrudates were dried at ambient conditions in hotcirculating air for 1 hour and then at 120° C. for 2 hours and finallycalcined at 500° C. for 2 hours. The catalysts obtained contained 5% wtof nickel and 21% wt of tungsten, weight of metal on total weight ofcatalyst.

Activity Testing

The hydrocracking performance of the catalysts was assessed in a numberof second stage series-flow simulation tests. The testing was carriedout in once-through microflow equipment which had been loaded with a topcatalyst bed comprising 1 ml C-424 catalyst (commercially available fromthe Criterion Catalyst & Technology Company) diluted with 1 ml of 0.1 mmSiC particles and a bottom catalyst bed comprising 10 ml of the testcatalyst diluted with 10 ml of 0.1 mm SiC particles. Both catalyst bedswere presulphided prior to testing.

Each test involved the sequential contact of a hydrocarbonaceousfeedstock (a pre-treated heavy vacuum gas oil) with the top catalyst bedand then the bottom catalyst bed in a once-through operation under thefollowing process conditions: a space velocity of 1.5 kg heavy gas oilper litre catalyst per hour (kg·l⁻¹·h⁻¹), a hydrogen gas/heavy gas oilratio of 1440 Nl/kg, a hydrogen sulphide partial pressure of 5.6×10⁵ Pa(5.6 bar) and a total pressure of 14×10⁶ Pa (140 bar).

The heavy gas oil used had the following properties:

-   Carbon content: 86.50% w-   Hydrogen content: 13.48% w-   Nitrogen (N) content: 14 ppmw-   Added n-Decylamine: 12.3 g/kg (equivalent to 1100 ppmw N)-   Total nitrogen (N) content: 1114 ppmw-   Density (15/4° C.): 0.8757 g/ml-   Density (70/4° C.): 0.8415 g/ml-   Mono-aromatic rings: 4.23% w-   Di+-aromatics rings: 1.35% w-   Initial boiling point: 359° C.-   50% w boiling point: 451° C.-   Final boiling point: 602° C.-   Fraction boiling below: 370° C.: 2.86% wt-   Fraction boiling above: 540° C.: 9.71% wt

Hydrocracking performance was assessed at conversion levels between 40and 90% wt net conversion of feed components boiling above 370° C. Theexperiments were carried out at different temperatures to obtain 65% wtnet conversion of feed components boiling above 370° C. in allexperiments by interpolation. Table 2 shows the results obtained. Theliquid product is the hydrocarbons which are liquid at ambientconditions. The cloud point is measured according to ASTM D2500.

TABLE 2 Catalyst 5 6 7 8 Zeolite Y (% wt) 30 30 22.5 22.5 Zeolite beta(% wt) — — 7.5 7.5 Carrier calcination (° C.) 620 750 620 750Temperature required (° C.) 378 380 378 379 Fraction boiling below 370°C. (% wt) C1-C4 4.6 2.9 3.4 3.3   C5-82° C. 9.9 7.0 9.8 8.9  82-150° C.23.6 22.4 23.4 21.2 150-250° C. 36.4 39.3 36.8 37.4 250-370° C. 25.528.4 26.6 29.1 150-370° C. 61.9 67.8 63.4 66.5 Cloud point of liquidproduct 36 37 16 15 Denitrogenation (% wt on feed) 97.0 98.5 96.9 98.2

That which is claimed is:
 1. A hydrocracking catalyst carrier obtainableby a preparation process comprising: calcining zeolite Y, having asilica to alumina molar ratio of at least 10, in the absence of addedsteam at a temperature in the range of from 700° C. to 1000° C. followedby mixing the obtained zeolite Y with an amorphous binder, comprisingsilica-alumina containing silica in an amount in the range of from 25 to95% by weight as calculated on the carrier alone, and an acidic aqueoussolution in amount so as to provide a mixture having a pH in the rangeof from 4.4 to 5.7 and an LOI in the range of from 50 to 65% such thatsaid hydrocracking catalyst carrier has a monomodal pore sizedistribution, wherein at least 50% of the total pore volume is presentin pores having a diameter in the range of from 4 to 50 nm; extrudingsaid mixture to give an extrudate; and calcining said extrudate at atemperature of from 700 to 1000° C.
 2. A hydrocracking catalyst carrierwhich comprises amorphous binder and zeolite Y having a silica toalumina molar ratio of at least 10, the infrared spectrum of whichcarrier has a peak at 3690 cm⁻¹, substantially reduced peaks at 3630cm⁻¹ and 3565 cm⁻¹ and no peak at 3600 cm⁻¹.
 3. A hydrocracking catalystcarrier which comprises amorphous binder and zeolite Y having a silicato alumina molar ratio of at least 10, which carrier has an acidity asmeasured by exchange with perdeuterated benzene of at most 20micromole/gram.
 4. A process for preparing a hydrocracking catalystwhich process comprises preparing a carrier according to claim 1, andsubsequently impregnating the calcined carrier with a Group VIII metaland a Group VIB metal.
 5. A hydrocracking catalyst obtainable by apreparation process according to claim
 4. 6. A hydrocracking catalystwhich comprises a Group VIII metal, a Group VIB metal and a carriercomprising amorphous binder and zeolite Y having a silica to aluminamolar ratio of at least 10, the infrared spectrum of which catalyst hasa peak at 3690 cm⁻¹, substantially reduced peaks at 3630 cm⁻¹ and 3565cm⁻¹ and no peak at 3600 cm⁻¹.
 7. A hydrocracking catalyst whichcomprises a Group VIII metal, a Group VIB metal and a carrier comprisingan amorphous binder and zeolite Y having a silica to alumina molar ratioof at least 10, which catalyst has an acidity as measured by exchangewith perdeuterated benzene of at most 20 micromole/gram.
 8. Ahydrocracking process for converting a hydrocarbon feedstock into lowerboiling materials which comprises contacting a hydrocarbon feedstock atelevated temperature and pressure with a hydrocracking catalystaccording to claim
 6. 9. A hydrocracking catalyst carrier obtainable bya preparation process according to claim 1.